Fan



D. G. SMELLIE Jan. 3, 1933.

FAN

Filed Jan. 24, 1929 IXVENTOR. fianale? Smellje A T TORNE Y.

Patented Jan. 3, 1933 UNITED STTES DONALD G. SMELLIE, OF CANTON, OHIO,ASSIGNOR TO THE HOOVER COMPANY, A CORPORATION OF OHIO FAN Applicationfiled January 24, 1929.

This invention relates to fans and more particularly to high speed fansand consists primarily in a new and novel fan structure adapted to beoperated at a high rate of 5 speed with efliciency and absence ofhowling heretofore present in high speed fans.

In the operation of an ordinary high speed fan, such as is found insuction cleaners, air is drawn into the fan chamber at the 10 center ofthe fan and fan chamber which is the low pressure point and is exhaustedat the periphery of the fan blades or high pressure area through anopening in the surrounding housing. With the fan revolving at a constantrate of speed the individual blades pass the point of cutoff, a point inthe fan chamber which the fan blade passes just after passing theexhaust outlet, at equal time intervals. The result of the con- 23tinued high frequency passing of the fan blades past this point ofcutoff is a howling noise or siren effect, caused by the vibration setup in the air acted upon within the structure itself. The fan structureforming the subjectmatter of the present invention is adapted toeliminate this high frequency howling at high speeds.

The principal object of thisinvention is a the provision of an eflicienthigh speed fan which will function with an absence of noise due tohowling or siren effect. It is a further object of this invention toprovide a fan constructed in a new and novel manner V which is adaptedto function at high speed within the ordinary fan chamber with absenceof noise.

Referring now to the drawing in which like reference characters refer tothe same parts throughout: 7

Figure 1 is a vertical cross section through a fan constructed inaccordance with this invention. I

Figure 2 is a bottom view of a fan constructed in accordance with thisinvention. Figure 3 is a bottomview of a modification of the presentinvention.

Figure 4 illustrates a fan constructed in accordance with the presentinvention, positioned in a common type fan casing.

Referring to Figure 1 in particular the Serial No. 334,625.

reference character 1 refers generally to a fan constructed inaccordance with this invention in which the body of the fan comprises arigid back or web 7 and central hub member 8. Positioned centrally ofthe fan and within the member 8 is the shaft 5 adapted to be connectedto a high speed center and so positioned that imaginary extensionsthereof are tangent to an imaginary circle described about the fan axis.Referring now to Figure 2 in particular the blades 2 of the fanconstructed in accordance with this invention are shown spaced apart byspaces 4 which are varied in :1.

definite manner, the angles between the blades I being varied by adecrement or increment 2A in a fixed sequence. The sequence of theangular arrangement of the blade is (Of A) (a+A), (dA), (a+A) etc.

In the operation of the ordinary fan, the blades pass the point ofcutoff of the fan chamber at high speed and are separated by very smalltime intervals. In Figure 4 of the drawing, a fan constructed as in thepresent invention, is shown embodied in a fan chamber 10, the point ofcutoff being indicated by the reference character 11. The result is ahigh frequency vibration of the surrounding air and chamber which isequal or proportional to the product of the R. P. M. of the fan timesthe number of fan blades (=R. P. M. N). The surrounding air is set intovibration at a certain frequency and as each succeeding blade reachesthe point of cutoff in synchronism with the period of vibration theresultis cumulative and the accompanying howling or siren efi'ect growsto an unpleasant degree. Withthe -fan constructed in accordance with thepresent invention the blades do not pass the point of cutofi' atconstant frequency or time intervals but'at unequal time intervals, theextent of which are determined by the increment or decrement A to theangle between successive blades. The result of this arrangement ofblades is to eliminate the cumulative effect present in fans havingblades equi-spaced. Each blade sets up a vibration of the surroundingair as it passes the cutoff point, the frequency of which is determinedby the time interval between its passing the cutofi point and thepreceding blade passing said point.

the sequence of angular displacement of the blades is (a) (aA), (a-l-A),(or) In such a construction the cancellation of vibrations isaccomplished by the proper selection of the angular lncrement delta.

In the present invention a new and novel fan is presented which isdesigned and adapted for high speed operation such as is found insuction cleaners. The design is such that under high speed conditionshigh frequency vibrations have been dampened resulting in theelimination of unnecessary, but heretofore ever present, high frequencyhowling or' siren effect in the operation of the fan. lhis result hasbeen accomplished without the sacrifice of fan efliciency or a radicaldeparture from standard fan construction;

I claim:

1. A fan comprising a body and fan blades carried by said body,characterized by the fact that said blades are tangent at their innerends to a common circle and by the fact that said blades are spacedunequally in a definite sequence.

2. A rotary fan comprising a body, and blades mounted on said body aboutthe axis of rotation, characterized by the fact that said blades aresubstantially alike and the included angle separating adjacent blades isvaried in the sequence (a), (on-A), (m+A), (01), etc.

'3. A fan adapted for axis comprising blades positioned about that axis,said blades being perpendicular to a common plane and separated byunequal angles differing by a definite angular increment.

4. A fan adapted for rotation about an axis comprising blades positionedabout that axis said blades being perpendicular to a common plane andseparated by unequal spaces differing by a definite increment, said 7spaces being arranged in a definite sequence.

5. A rotary fan comprising a web adapted for rotation about an axisperpendicular to rotation about an said web, and fan blades carried bysaid web positioned about said axis of rotation, said fan beingcharacterized by the fact that said blades are spaced unequally in adefinite sequence.

6. A centrifugal fan comprising a body and fan blades carried by saidbody, characterized by the fact that said blades are tangent at theirinner ends to a common circle and by the fact that said blades arespaced unequally in a definite sequence.

Signed at North Canton, in the county of Stark and State of Ohio, this12th day of January, A. D. 1929.

. DONALD G. SMELLIE.

